和为S的连续正数序列_41

public ArrayList<ArrayList<Integer>> FindContinuousSequence(int sum) {
        ArrayList<ArrayList<Integer>> res=new ArrayList<>();

        int leftIndex = 1;
        int rightIndex = 2;

        while (rightIndex>leftIndex){
            int curSum=(leftIndex + rightIndex) * (rightIndex - leftIndex + 1) / 2;
            if (curSum>sum){
                leftIndex++;
            }else if (curSum<sum){
                rightIndex++;
            }else {
                ArrayList<Integer> item=new ArrayList<>();

                for (int i = leftIndex; i <=rightIndex ; i++) {
                    item.add(i);
                }
                res.add(item);

                leftIndex++;
            }
        }

        return res;
    }